This invention relates to batteries.
Batteries, such as alkaline batteries, are commonly used as energy sources. Generally, alkaline batteries include a cathode, an anode, a separator, and an electrolytic solution. The cathode is typically formed of an active material (e.g., manganese dioxide), carbon particles, and a binder. The anode can be a gel including an active material (e.g., zinc particles). The separator is usually disposed between the cathode and the anode. The electrolytic solution, which is dispersed throughout the battery, can be a hydroxide solution.
Alkaline batteries include the conventional AA, AAA, AAAA, C, and D batteries commonly sold in stores. These conventional alkaline batteries include a cylindrical container containing a central, cylindrical zinc gel anode surrounded by a ring-shaped manganese dioxide cathode.
It generally is desirable for a battery to have a long service life. One measure of the service life of a battery is the length of time the battery can discharge under a given load before the voltage drops to an unacceptable level.
The invention relates to a battery having a good service life when discharged continuously, for example, at 1 amp. The good service life is provided by including a high interface area between the cathode and the anode in the battery.
One way to provide a relative measure of interface area between the anode and the cathode is to approximate the xe2x80x9ceffective thicknessxe2x80x9d of the cathode. For a particular battery (e.g., a AA battery), the smaller the cathode thickness, the greater the interface area per cathode volume. The relative effective thickness of a cathode can be estimated by using the equation (S/V)2 where S is the separator surface area and anode and V is the cathode volume.
In another aspect, the invention features a AA battery in which (S/V)2 is greater than 0.38, preferably greater than 0.40, and more preferably greater than 0.42 or 0.45.
In another aspect, the invention features a AAA battery in which (S/V)2 is greater than 0.70, preferably greater than 0.75, and more preferably greater than 0.80 or 0.82.
In another aspect, the invention features a AAAA battery in which (S/V)2 is greater than 1.2, preferably greater than 1.3, and more preferably greater than 1.4 or 1.5.
In another aspect, the invention features a C battery in which (S/V)2 is greater than 0.110, preferably greater than 0.120, and more preferably greater than 0.125 or 0.130.
In another aspect, the invention features a D battery in which (S/V)2 is greater than 0.65, preferably greater than 0.70, and more preferably greater than 0.75, 0.80, 0.9, or 1.0.
In another aspect, the invention features a AA battery including a single cavity anode within the cathode. The (S/V)2 of the battery is greater than 0.15, preferably greater than 0.20, and more preferably greater than 0.30, 0.35, or 0.40.
In another aspect, the invention features a AAA battery including a single cavity anode within the cathode. The (S/V)2 of the battery is greater than 0.3, preferably greater than 0.4, and more preferably greater than 0.5 or 0.6.
In another aspect, the invention features a AAAA battery including a single cavity anode within the cathode. The (S/V)2 of the battery is greater than 0.6, preferably greater than 0.8, and more preferably greater than 1.0, 1.2 or 1.5.
In another aspect, the invention features a C battery including a single cavity anode within the cathode. The (S/V)2 of the battery is greater than 0.06, preferably greater than 0.08, and more preferably greater than 0.09, 0.10, or 0.11.
In another aspect, the invention features a D battery including a single cavity anode within the cathode. The (s/v)2 of the battery is greater than 0.03, preferably greater than 0.04, and more preferably greater than 0.05, 0.06, 0.07, or 0.08.
In another aspect, the invention features a battery including a cylindrical housing, a first electrode, and a one-cavity second electrode within the first electrode. The battery has a (S/V)2/cathode OD vs. cell diameter value of at least 0.01, more preferably at least 0.02, and most preferably at least 0.03 or 0.04, above Plot A, which is subsequently defined.
In another aspect, the invention features a battery including a cylindrical housing, a first electrode, and a second electrode within the first electrode. The battery has a (S/V)2/cathode OD vs. cell diameter value of at least 0.01, more preferably at least 0.02, and most preferably at least 0.03 or 0.04, above Plot B, which is subsequently defined.
Preferably, the batteries described above have a cathode including manganese dioxide and an anode including zinc.
In some preferred embodiments, one electrode (e.g., the anode) includes a lobed cavity within the other electrode. The lobed cavity may include, for example, two, three, four, five, or nine lobes. In fact, in another aspect, the invention features a battery including a nine-lobed electrode.
In other preferred embodiments, one electrode (e.g., the anode) includes multiple cavities within the other electrode. For example, the multiple cavities may include cylindrical cavities, D-shaped cavities, or pie-shaped cavities. The cavities may be connected by a narrow connecting portion.
Other features and advantages of the invention will be apparent from the description of the preferred embodiments thereof, and from the claims.